Resistive adjunct device and component



June 3, 1969 J. R. BASKETT 3,448,427

RESISTIVE ADJUNCT DEVICE AND COMPONENT Filed Dec. 4, 1967 R FIG. Z

I INVENTOR.

JH/v A. BASKETT United States Patent 3,448,427 RESISTIVE ADJUNCT DEVICE AND COMPONENT John R. Baskett, Riverside, Calif., assignor to Bourns, Inc., a corporation of California Filed Dec. 4, 1967, Ser. No. 687,652 Int. Cl. H01c 5/02 US. Cl. 338-162 8 Claims ABSTRACT OF THE DISCLOSURE In copending application for Letters Patent Ser. No. 628,890, now US. Patent No. 3,380,011 filed April 6, 1967, there is disclosed an inexpensive novel miniature adjustable resistor of generally cylindrical configuration which comprises a variable resistive component connected with a fixed-value resistive component and which permits, inter alia, stocking of one range-value of resistor instead of a large number of conventional fixed-value resistors, and which further permits easy and accurate adjustment of the effective resistance value after the resistor is incorporated in an electronic circuit. In copending application for Letters Patent Ser. No. 628,889, now US. Patent No. 3,377,605 filed April 6, 1967, there is disclosed a novel miniature single-turn rotary potentiometer of external configuration similar to that of the adjustable resistor disclosed in the noted application Ser. No. 628,890, but comprising three terminal members. Both of the noted circuit components are so constructed as to permit simple plugging-in and soldering-in-place in circiut board constructions. The present invention provides a novel adjunct to adjustable resistive components of those types, and one which permits attainment of a variety of extensions or modifications of the ranges, functions, and utility of those components, and in one form permits conversion of a potentiometer into an adjustable resistor with capability of rapid reconversion of the potentiometer to original form and functioning. All such changes are accomplished easily, and without increase in the amount of circuit-board area required.

The noted novel results, and others that are hereinafter made evident, are attained by the present invention by provision of a special resistive structure comprising a perforated fiat thin plate or wafer of insulation dimensioned to match the base and pin configurations of adjustable resistive components of the noted type and to be pressed onto and receive terminal pins thereof and to thus underlie and be electrically connected to the component and mechanically integrated therewith. The adjustable resistive component and the adjunct device form a versatile combination device for use on a circuit board. The flat thin plate of insulation comprised in the novel adjunct device according to the invention is preferably of circular disc configuration, but as will be evident, it may be of square, octagonal, hexagonal or other plan form. It further is preferably of ceramic material such as alumina or steatite. The apertures and tubular conductive means therein are proportioned and disposed so as to directly receive conductive terminal pins of the compatible adjustable resistive component, whereby the integrated structure may be disposed on an apertured circuit board or panel with the two integrated members in superposed relation.

Further, the construction of the novel adjunct device is such that resistive means thereof, of which there may be one disposed on each of the respective faces of the disc or wafer, may be variously disposed with respect to the terminal pins of the adjustable resistive component superposed thereon so as to modify in either of alternative ways the resistive value, the functional operation, and/or the utility of the principal component. For example, in one electrical form, the adjunct device of the invention greatly enhances the functional operation of a mating potentiometer with which it is mechanically and electrically combined, while concurrently furnishing an absolute guarantee against open-circuit caused by potentiometer contact burn-out. As another example, in a generally similar electrical form, the adjunct device may be utilized to greatly increase the total resistance range of the adjustable resistor with which it is mated, or to considerably change the accuracy of resistance value setting thereof.

The previously mentioned adjustable resistor is disclosed as having two terminal pins extending in parallel relationship from the bottom face of the base thereof, whereas the mentioned variable potentiometer comprises three such terminal pins. In either of those components two of the pins emerge from the base at respective points on a diameter of the base and are on a center-tocenter modular spacing compatible with that of the apertures of an apertured circuit board. The latter apertures may, for example, be in rows and columns spaced onetenth (0.1) inch on centers. Thus the terminal pins of the two noted resistive components are correspondingly spaced, for example, one-tenth inch apart, each from the nearest other one thereof, so as to be easily plugged or pressed into apertures of a circuit board.

Since the adjunct device comprised in the present invention must generally receive and have passed through apertures thereof, respective pins of that one of the mentioned adjustable resistive components which is to be electrically modified by the adjunct device, the noted apertures are arranged to be compatible with those of the circuit board and with the pine of the selected mating principal component. In one form of the invention, only two apertures need be formed in the wafer or plate of the adjunct device; in others, three or four such apertures, as will later herein be made evident. As a matter of convenience in manufacturing, all of the adjunct device wafers may be made with the same number of apertures, those not necessary in a particular form of the device being left unused or idle. The apertures are made to have conductive walls, preferably with the addition of tubular eyelets pressed into place and secured therein, the openings or bores of the eyelets being dimensioned and formed as required to receive the terminal pins of the components with good mechanical and electrical integration as will be more explained hereinafter. Further, each of the novel adjunct devices carries on one or both face surfaces thereof, appropriate conductive and resistive deposits or coatings, connecting selected aperture eyelets or conductors and arranged and disposed according to the particular function to be performed, as will later herein be described in detail. Also, the devices may comprise insulative coatings or covers in the form of adherent jackets overlying the resistive and conductive deposits or coatings, and may further comprise feet or stand-off spacing means, as will later be described.

The preceding general description of characteristics of the invention indicate that it is broadly an object of the invention to provide an adjunct device for adjustable resistors and potentiometers whereby to enhance characteristics and utility thereof.

Another object of the invention is to provide an adjunct device or accessory for an adjustable resistive component such as an adjustable resistor or potentiometer for efiecting improvements in functional operation of the resistive component.

Another object of the invention is to provide a simple inexpensive resistive device usable in direct mechanical and electrical combination with an adjustable resistive component such as an adjustable resistor or potentiometer, to enhance the electrical and operational characteristics of the component.

An additional object of the invention is to provide an adjunct device for an adjustable pin-mounted resistive component which may be concurrently mechanically and electrically integrated with the latter component in stacked relationship therewith whereby to enhance electrical and operational characteristics of the adjustable component without requiring additional mounting space on a circuit board.

Another object of the invention is to provide a resistive accessory for an adjustable resistive component capable of direct mechanical and electrical integration with the component and effective to preclude catastrophic failure due to contact burn out or open-circuit at the contact of the component. I

Other objects and advantages of the invention are hereinafter set out or made apparent in the appended claims or in the following detailed description of a pre ferred exemplary and illustrative physical embodiment of the invention and exemplary electrical variations thereof, as illustrated in the appended drawings forming a portion of this specification. In those drawings:

FIGURE 1 is a pictorial representation of a miniature variable resistive component and mechanically and electrically integrated therewith an adjunct device or accessory, according to the invention, the view being grossly enlarged to facilitate illustration of detail;

FIGURE 2 is a side view partly in section, of components of the adjunct device depicted in combination with a miniature variable resistive component in FIGURE 1, and to larger scale;

FIGURE 3 is a face view of the exemplary adjunct device shown in FIGURE 2, with an insulation jacket or cover removed, illustrating details of internal structure of the adjunct device;

FIGURE 4 is a side view, similar to FIGURE 2 but not sectioned, of an adjunct device comprising two resistive elements on respective opposite faces of the device;

FIGURE 5 is an upper face view of the device depicted in FIGURE 4, with the insulative jacket or coating removed;

FIGURE 6 is a bottom face view of the adjunct device depicted in FIGURE 4, with the insulative jacket removed;

FIGURES 7 and 8 are upper face views of adjunct devices according to the invention, showing exemplary alternative configurations or arrays of conductive and resistive means;

FIGURE 9 is a sectional view illustrating features of an exemplary conductive aperture in an adjunct device according to the invention;

FIGURE 9a is a sectional view illustrating one mode of facilitating application of an insulative jacket or coating on a completed substrate assembly in manufacturing an exemplary adjunct device such as is depicted in FIGURES 1 and 2; and

FIGURES 10, 11, 12 and 13 are groups of schematic diagrams, each illustrating the scheme for electrically and mechanically integrating an adjustable resistive electronic component and an exemplary adjunct device, and schematically depicting the respective electrical interconnection of resistive elements effected by the integration.

.Referring first to FIGURE 1, there is shown a miniature component 12 which comprises a plurality of terminal means including terminal pins R and G, and a rotatable member 14 by the rotation of which the value of electrical resistance exhibited between two or more of the terminal means may be varied or adjusted The component 12, which may be of the type disclosed in either of the aforementioned patent applications, or of similar character and having two or more pin terminals, is mechanically and electrically integrated with :an adjunct device 20 on which it is superposed. Integration is accomplished by pressing the ends of the terminal pins of the component through respective conductive means dis posed in complementary apertures provided through the adjunct device, whereby there is formed a unitary device or unit 10. The exact nature of an exemplary component 10 is ascertainable from the disclosures of the two previously-mentioned applications for patent, to which disclosures reference may be had as may be required for a complete understanding of those inventions. Those disclosures are incorporated herein for reference purposes. If desired, electrical and mechanical integration of the devices comprised in unit 10 may be enhanced by application of free-flowing solder to the terminal pins, as will presently be more fully explained.

The adjunct device 20 in exemplary basic form comprises essentially a thin wafer or substrate of insulation having a plurality of through-holes or apertures arranged in a spatial array which is congruent to or compatible with the pin array of the component 12 and preferably also with the spatial array of apertures in a standard apertured circuit boar-d. An example of board of the type contemplated is a plugboard of Type 812 marketed by Vector Electronics Co., Inc., Glendale, Calif., 91201. The adjunct device further comprises essentially conductive means in each of the apertures and conductive and resistive elements disposed on one or both faces of the wafer. The conductive and resistive elements are in the form of thin films or coatings, of materials exemplary ones of which are defined hereinafter in detail, and may be disposed in a variety of patterns or areal configurations depending upon the electrical elfect to be produced.

A typical exemplary adjunct device 20 is shown partly in section in FIGURE 2; and is shown in plan view with the insulative and protective jacket or insulation I removed, in FIGURE 3. Referring to those figures, 20w designates a thin fiat wafer or substrate of insulation such as ceramic alumina or steatite. The wafer 20w is preferably of circular disc form, but may be of rectangular or other plan form shape, as noted. Four through-holes (hereinafter called apertures), such as G, R and Y are provided, arrayed according to a selected aperture-grid modulus as previously noted and here shown, by way of example, according to a square-grid modulus. Disposed on the upper face of wafer 20w and continuing on into and through the interiors of respective ones of the apertures are conductive films or elements, F1, F2 and F3. The conductive films may be produced, for example, by known process including painting or silk screening a silver paint on the desired areas, followed by firing. However, other known processes may be followed. Interconnecting conductive elements F2 and F3 is a resistive element X1, as hereinafter described. Conductive element F1 extends into both of apertures G and R, whereas element F3, for example, extends into only aperture Y and over a surface of the wafer as indicated, and element F2 extends into only aperture B.

Continuing with reference to the exemplary adjunct device illustrated in FIGURES 2 and 3, each of the four apertures shown has afiixed therein and extending therethrough a respective conductive tube or eyelet such as that illustrated in section in FIGURES 9 and 9a and labeled 20:2. The tubular conductive members or eyelets are formed of ductile material such as brass, and are pressed or spun over at their ends as indicated in FIG- URES 9 and 9a, whereby contact is made with a generally circular area of one or another of the conductive elements such as F1, F2 and F3. Further, to enhance electrical and mechanical contact of the eyelet with the conductive element or film on the interior vwall of an aperture, the tubular stock or material of which the eyelets are made may be drawn with longitudinally extending ridges or lands on the exterior of the stock. Also, similar longitudinally extending ridges or lands, such as that labeled 20r in FIGURE 9, may be provided along the interiors of the eyelets, for purposes presently explained. The eyelets are not essential to the invention but materially enhance firm and effective electrical and mechanical connection of component terminal pins with the conductive films on the wafer. The eyelets are thus accurately dimensioned to receive respective pin terminals, such as pin terminals R and G of component .12 shown in FIG- URE 1, or an adjunct device stub terminal pin such as that labeled B in FIGURE 3. The latter pin terminal does not extend above the upper face of the wafer 20w but protrudes below the lower face and is adapted to be received in one of the modular apertures of a circuit board or plug board. In certain cases, such stub terminal pins may be fired in situ in the wafer if the latter is of ceramic material, or may be molded in situ when the wafer is of molded synthetic resin or the like. As is evident, when .pin terminal devices such as terminal pins R and G of component 12 (FIGURE 1) are passed or pressed through respective ones of eyeleted apertures R" and G of the adjunct device 20, and also are passed through respective apertures in a compatible circuit board, the assembly maybe subjected to a conventional dipsoldering procedure or other soldering procedure. During the procedure, molten solder flows into the apertures (or into the eyelets), entering between the terminal pins and the eyelet wall or conductive film, such flow being aided by the noted internal ridges or lands in the eyelets, and thus greatly enhances the electrical and mechanical integration or connection of the adjunct device and the component 12.

The adjunct device depicted in FIGURES 2 and 3 further comprises a resistive film, layer or coating form ing the noted resistive element X1. The resistive and dimensional characteristics, and material of which element X1 is composed, may be widely varied, depending upon the effect it is desired to accomplish in conjunction with the resistive means of component 12. These matters are more fully explained hereinafter, with citation of specific examples. Thus, for example, resistive element X1 extending between conductive elements F2 and F3 may be formed of a cermet composition, or of conductive plastic material; and may be of width, thickness, length and electrical resistivity to provide or exhibit an electrical resistance value of desired magnitude between aperture Y' and the stub terminal pin B.

Exemplary resistive compositions, in addition to cermets, examples of which are disclosed in U.S. Patent No. 3,149,002, include carbon-in-resin, carbon film, carbon and metal as disclosed in U.S. Patent No. 3,107,179, metal films, metal nitrides, and the like. Exemplary conductive films or coatings such as those labeled F1, F2 and F3 are preferably produced by application of metal paste or paint such as silver paint, or organo-metallic materials. Such pastes or paints are applied by painting, or may be printed or silk-screened into position, and are fired to produce permanent adherent films. The techniques or processes of applying the resistive and conductive elements, and the materials that may be used, are various and are generally well known to persons skilled in the electrical resistor art, and are therefore not herein further described.

Other styles or areal arrays of resistive elements and conductive elements may equally well be utilized in the production of adjunct devices according to the invention, with a variety of enhancements of the electrical characteristics of the electrical resistive components with which the adjunct devices are adapted to be electrically and mechanically integrated. Other representative styles or areal configurations of conductive and resistive elements are illustrated in FIGURES 5-6, 7 and 8; and following brief descriptions thereof, the advantages and novel results attained by the adjunct device bearing conductive and resistive element patterns illustrated in FIGURES 3, 5-6, 7 and 8 will be explained in connection with respective ones of FIGURES l0, 11, 12 and 13.

In FIGURES 4, 5 and 6 there is illustrated an adjunct device according to the invention, which comprises as a substrate an insulation Wafer 20w which on its upper (top) face and its lower (bottom) face bears respective and different patterns or arrays 20B and 20B of conductive and resistive elements, either or both of which arrays may be used and electrically and mechanically integrated with a resistive component 12. The basic physical structure or foundation of the adjunct device, including the insulation wafer 20w with apertures G, R, Y and B and eyelets, such as 20e, but omitting pin B and the resistive and conductive elements, is or may be substantially identical with the corresponding structure previously described in connection with FIGURES 2 and 3. Apertures R and B bear internal conductive films and contain respective conductive eyelets which electrically connect with conductive-coating elements F4 and F5 (FIGURE 5), respectively. Apertures G and Y bear internal conductive films and contain respective similar etyelets such as 20e which electrically connect with conductive-coating elements F6 and F7 (FIGURE 6), respectively. Conductive elements F4 and F5 of the array 20B are electrically interconnected by a resistive element X2, which may be substantially identical with or similar to element X1 described in connection with FIGURE 3. Conductive elements F6 and F7 are electrically interconnected by a resistive member or element X3 (FIG- URE 6) which may be similar to resistive element X2 but of different terminal-to-terminal resistance value, or of different temperature coefficient or other electrical characteristic. The reasons for the latter will presently be explained in connection with FIGURE 11, as will the electrical functions of the arrays 20B and 20B.

In FIGURE 7 there is illustrated the upper face of an adjunct device according to the invention, with an insulative jacket or coating removed, depicting an array 20C of conductive and resistive elements interconnecting certain ones of the conductive eyeleted apertures. The basic physical structure or foundation of the adjunct device, including the apertured insulation wafer 20w, the aperture eyelets such as 202 and conductive coatings in. the apertures, is or may be substantially identical with the corresponding structures previously described in connection with FIGURES 3 and 5-6. Aperture G bears a conductive film connected with the eyelet therein and with an applied conductive element F8; and aperture B is similarly equipped with an internal conductive film and an eyelet connected with an applied conductive film element F9. The array 20C includes a resistive element X4 which may be of the nature of the previously described element X3 and which electrically interconnects conductive elements F 8 and F9. As in the case of the adjunct devices depicted in FIGURES 2 through 6, the exposed surfacespf wafer 20w preferably bear an insulation coat or jacket which has been removed for convenience in illustration. The eyelets and conductive film in apertures R and Y serve no direct electrical function in respect of array 20C, but serve in performance of the function of effecting mechanical integration and coordination with respective terminal pins of the compatible electronic component 12. The function of resistive element X4 will hereinafter be explained in connection with FIGURE 12. As in the case of the adjunct device illustr-ated in FIGURE 3, the similar device of FIGURE 7 preferably has added thereto as a part thereof a stub terminal pin B in the aperture B. The stub terminal pin, while not essential to the invention, may be added during any of various stages of manufacture of the device. It serves, when used, to facilitate electrical connection of element F9 to an external electrical circuit borne by the plug board, for example, and to augment mechanical integration of the adjunct device and such circuit. When the stub terminal is not used in the embodiment illustrated in FIGURE 7, a wire-end, or solder flowed into the aperture B is effective to perform the necessary electrical connection. However, use of the stub terminal B is obviously advantageous in most applications of the conductive-resistive arrays 20A and 20C.

In FIGURE 8 an adjunct device with its insulative cover removed is depicted in plan form, bearing an array 20D comprising conductive elements F10 and F11 and a resistive element X electrically interconnecting the conductive elements. The adjunct device comprises insulation wafer 20w having apertures G, R, Y and B, at least R and Y of which are each bounded by a conductive coating and bear a conductive eyelet such as 20a. The eyelet in aperture R is in electrical communication with the conductive layer or film element F10, and the eyelet in aperture Y is in electrical communication with conductive element F11. The noted apertured wafer and eyelets are similar in most respects to those described in connection with wafer 20w of FIGURES 2 and 3, and the elements F and F11 may be similar to corresponding elements F8 and F9 of FIGURE 7 except as to areal configuration. As is evident the resistance value of element X5 may be of any of various values in a wide range thereof, that being a matter of choice of design and material composition. As illustrated, in exemplary form only, the resistive element X5 is of resistance wire wound on a mandrel or card and alternatively disposed on the surface of the wafer in those instances wherein a thin flat card or mandrel is employed, or disposed in a cavity or hole formed in the water in those instances wherein a cylindrical mandrel is used. In either type, the resistance wire is welded or soldered at its ends to respective ones of the conductive elements. As is evident to those skilled in the electrical resistor arts, vvire composition, size, length, etc. are matters of design susceptible of considerable variation within the skill of the artisan and are accordingly not herein further treated.

It is evident from the preceding description that the adjunct device according to the invention comprises basic structural means or members having like physical characteristics irrespective of the pattern or array of conductive and resistive elements contained on the apertured insulation wafer. The particular arrangement of conductive and resistive elements employed depends upon such factors as the basic nature and construction of the resistive electronic component with which the adjunct device is to be integrated and serve, and the nature of the modification and enhancement it is desired to effect in the operational and electrical characteristics of the resistive component. Thus, desirable modifications and enhancements which result from integration of the exemplary adjunct devices comprising arrays A, 20B, 20B, 20C and 20]) with one or another of the exemplary adjustable resistive electronic components described in the aforementioned patents, will be detailed with reference to FIGURES 10 through 13.

Referring to FIGURE 10, the component 12 is depicted as having tenminal pins G and Y and as being constructed with resistive elements Z1 and Z2 connected as indicated on the base of the component. The adjunct device 20, bearing the element array 20A as previously described, and equipped with a stub terminal pin B in aperture B, is indicated in position to receive in apertures G and Y respective terminal pins G and Y of component 12 and to thus be electrically and mechanically integrated with the component. When so integrated by stacking or superposition, the electrical network comprising elements Z1 and Z2 is modified to present a three-terminal network including element X1, as depicted in the diagram at the lower part of the figure.

Continuing with reference to FIGURE 10, and assuming, for example, that component 12 is an adjustable resistor such as that disclosed in the aforementioned application Ser. No. 628,890, it is evident that the total resistance value available has been increased by that of element X1, by utilizing pins G and B as the output or active terminals. Several unobvious results of merit are obtained by this modification of the electrical circuitry of the component 12, which may be the adjustable resistor disclosed in application Ser. No. 628,890, as well as the obvious increase in total resistance value. These advantages include: (a) a considerable logistical economy in inventory requirements of resistors to cover a range of total resistance (TR) values within any given resistance tolerance specification and settability specification, (b) improvement in precision of adjustment (settability) of the TR to a desired value, and (c) the ability to grossly increase the TR of a resistive device on a circuit board without increase of board space required, with concurrent improvement of precision of setting the TR value. The following explanation, with examples, will serve to illustrate the advantages. Due to the relatively low cost of adjunct devices as disclosed (e.g., one-fifth the cost of an adjustable resistor of the plug-in type such as component 12), an extremely wide range of resistor values may easily be covered, with equal or better precision as compared to precision fixed resistors; and any particular required resistance value within the range accurately anticipated by one component 12 integrated with one or another of less than a half-dozen adjunct devices.

For example, using a component 12 of resistive value adjustable from 2K ohms to 10K ohms, superimposed upon an adjunct device 20 of 200K ohms value, and using the electrical arrangement illustrated in FIGURE 10', the resistance value between terminals G and B may be accurately selected to be any value within the range 202K ohms to 210K ohms. Further, no careful selection of fixed-value resistors is required, and no additional circuitboard space is required. When the electrically and mechanically integrated component 12 and device 20 are plugged into a circuit after only an approximate selection as to resistance values, the component 12 can be adjusted in situ to bring the resistance value to exactly that required in the circuit. When it is considered that such circuit components as transistors present variations which require trial measurements and repetitive selection and trial of resistors of the fixed-value type if the circuit is to perform properly and efficiently, and that such selection and trial involve tedious and time-consuming operations, the advantages of having a component which can be quickly selected to only approximately anticipate the circuit requirements and then easily plugged in and brought to the proper value, are readily appreciated. Those advantages, coupled with the ability of the arrangement according to the invention to accurately anticipate any resistance value over a relatively enormous range of values, with only one adjustable component 12 and a few inexpensive adjunct devices 20, greatly reduce the time and stock of resistors required for accurate circuit construction. As is evident, further, the matter of heat dissipation is improved by the division of the heat generated between the component 12 and the adjunct device 20.

For convenience, adjunct devices bearing conductiveresistive arrays 20A and 20C are provided with auxiliary (stub) terminal pin meanssuch as conductive pin B which is preferably permanently rnounted in the eyelet or fused in aperture B. As is evident, the protruding portion of terminal pin Y may, in applications of the combination depicted in FIGURE 10, be severed from the integrated structure comprising component 12 and device 20. Such severance may be effected either before or following, plugging-in on a circuit board.

Further, as is made evident by consideration o f-FIG- URE 11, the combination of an adjustable resistive component 12 as indicated, with an adjunct device 20 bearing resistive elements X2 and X3 on respective opposite faces, to provide a circuit arrangement as indicated, perinits reduction of the TR exhibited between terminals while concurrently greatly improving the settability or precision of adjustment of the resistance value. Further, since with a single adjunct device a choice of either of two different resistance values (X2. and X3) to be combined in parallel with the resistive means of component 12 is presented, it is evident that two sets of ranges of resistance values are capable of accurate accommodation by the combination. As is evident, the parallel connection of the active resistive members of component 12 and device 20 reduces the resistance range and TR exhibited between tenminals G and Y. Thus, with a specific adjustable component 12, the TR may be increased, or decreased, dependent only upon choice of adjunct device.

Utilization of an adjunct device according to the invention with an adjustable resistive component 12 of the type described in the afiorementioned pending application Ser. No. 628,889, permits amplification or extension of the uses and utility of such component. For example, as indicated in FIGURE 12, the adjunct device may be equipped with :a stub terminal pin B (as previously noted in connection with FIGURE and with the array 200 of resistive and conductive elements. When electrically and mechanically integrated, the combination provides the adjustable circuit indicated at the bottom of FIGURE 12. Consideration of that circuit makes it evident that the resistive range of adjustment afforded by component '12 has been compressed with increase of resolution. As will be evident to those skilled in the art, the combination thus provided permits, with appropriate switching means, alternative easy selection of a wide adjustment range or a narrow adjustment range, tour terminal pins being available for circuit connection to the switch means.

Utilizing an array 20D of resistive and conductive elements on the adjunct device, as illustrated in FIGURE 13, permits ready conversion of a component 12 of the potentiometer type to an adjustable resistor, as is made evident in the circuit diagram at the bottom of that drawing. As is evident, an adjunct device such as depicted in FIGURE 13 may be utilized as that indicated in FIGURE 12 by the simple addition of a stub terminal pin B in the aperture R; and, conversely, by removal of the stub terminal pin B from the adjunct device of FIGURE 12 and proper mating of pins with apertures, the adjunct device of FIGURE 12 may be used as is the similar device of FIGURE 13. Other variations and extensions according to the invention are obvious, such as, for example, utilizing more complex arrays of apertures and conductive and resistive devices in the adjunct device.

Several procedures may be followed in applying the insulative and protective jacket or coating I (FIGURE 9) to adjunct devices according to the invention. For example, removable plugs, such as the elastic plug P (FIG- URE 9a) may be inserted into the eyelets following application of the conductive and resistive elements and installation of the eyelets, and the wafer then dip-coated with self-curing insulative resin. [Following curing of the resin, the plugs are withdrawn, leaving the eyelet bores ready for reception of terminal pins as described. Alternatively, the finished wafer may be placed in suitable die means equipped with eyelet-protecting pins, and the insulative jacket applied by injection-molding techniques.

In the light of the preceding disclosure of specific exemplary applications of the adjunct device, it is evident that further modifications of the electrical characteristics of a mechanically compatible variable resistive component, such as component 12, can be eifected by superpositioning of one or more additional adjunct devices on the pins of the resistive component, whereby a stack of two or more iadjunct devices is mechanically and electrically integrated with the component. As is evident, no additional board space is occupied by the resulting unit, irrespective of the number of adjunct devices employed.

The preceding detailed description of a presently preferred form of the invention and of exemplary applications thereof makes it evident that the aforementioned objects of the invention have been fully attained. In the light of the disclosure, modifications within the true spirit and scope of the invention will be suggested to others and hence I do not wish the invention to be restricted to exact details of the illustrative exemplary form of the invention except as is required by the appended claims.

I claim:

1. An adjunct resistive device adapted for electrical and mechanical integration with a variable resistive component having at least first and second pin terminals, said adjunct device comprising, in combination:

a wafer having an electrically insulative portion and said water having first and second opposite faces and having a plurality of spaced apertures therethrough from face to face thereof, at least two of said apertures being spatially disposed to receive respective ones of first and second pin terminals of such variable resistive component;

conductive element means carried by said water, said conductive element means comprising at least a first conductive means disposed at least in part in a first one of said apertures and a second conductive means spaced and insulated from said first conductive means by said insulative portion and disposed in part in another one of said apertures, said conductive means permitting entrance of pin terminals into respective ones of said apertures to permit concurrent electrical and mechanical connection therewith; and

resistive element mean-s carried by said wafer, said resistive element means comprising a resistive element electrically interconnecting a selected one of said conductive means with another thereof;

whereby said adjunct device may be concurrently mechanically and electrically integrated with a variable resistive component as an adjunct thereto by passing pin terminals of the component through respective ones of said spaced apertures and with at least one such pin terminal in contact with a respective one of said conductive means, to resistively modify the resistive component and form therewith an integrated variable resistive unit.

2. An adjunct resistive device as defined in claim 1, in which said apertures in said wafer are at least four in number, and in which adjunct device said first and second conductive means are disposed at least in part in respective first and second ones of said apertures and in which said resistive element electrically interconnects said first and second conductive means, and in which adjunct resistive device third and fourth conductive means are carried by said wafer each insulated from the other by said insulative portion and each disposed at least in part in a respective one of the third and fourth of said apertures, and in which said resistive element means comprises a second resistive element electrically interconnecting said third and fourth conductive means,

said resistive elements differing in an electrical characteristic,

whereby mechanical and electrical integration of said adjunct device with the variable resistive component may be efiected alternatively in either of first and second configurations to provide, alternatively, difiering electrical combinations.

3. An adjunct resistive device as defined in claim 1, in

which said apertures are at least three in number, and in which adjunct resistive device a stub terminal pin is 1 1 afiixed in the said first of said apertures of said wafer, said stub terminal pin extending away from one of said faces of said wafer and being electrically andmechanically integrated with said firstconductive means.

4. An adjunct resistive device as defined in claim 1, in which said wafer is composed essentially of electrical insulation, and in which device said first conductive means and said second conductive means comprise respective metallic tubular eyelets each extending through a respective one of said apertures and each secured to said wafer;

5. An adjunct resistive device as defined in claim 1, said device further comprising an insulative protective jacket over exterior surfaces of said wafer whereby to insulate and, protect said resistive element means.

6. An adjunct resistive device as defined in claim 1, in which device said resistive element is a thin cermet layer adherent to a face of said wafer.

7. An adjunct resistive device as defined in claim 1, in which device said resistive element is essentially a resistance wire.

8. A variable resistive unit comprising:

first means, including a variable resistive component having a resistance element and at least first and second terminal pins and means for varying the electrical resistance exhibited between said terminal pins, and second means, including a resistive adjunct device electrically and mechanically integrated with said variable resistive component, said adjunct device comprising a wafer having upper and lower faces and having a plurality of apertures therethrough from face to face, said first and second terminal pins of said resistive component extending through respective ones of said apertures of said wafer, said wafer carrying first and second conductive means at respective ones of a first and another of said apertures and at least one of said conductive means being in electrical contact and mechanical engagement with a respective one of said terminal pins, and said wafer carrying a resistance element electrically connected between said first and another of said conductive means,

' whereby the adjunct device is mechanically and electrically integrated with said variable resistive component to electrically modify the latter and to form therewith an integral unit for unitary handling and use.

References Cited UNITED STATES PATENTS 3,202,952 8/1965 Rayburn 338-308 3,377,605 4/1968 Baskett 338-162 3,380,011 4/1968 Baskett 338-162 LEWIS H. MYERS, Primary Examiner.

G. P. TOLIN, Assistant Examiner.

US. Cl. X.R. 338-262, 308 

